The invention relates to an electric motor regulating and control drive.
Such a drive is disclosed in German patent publication DE-OS No. 32 23 379 (corresponding to U.S. Pat. No. 4,556,132). Especially when such drives are used in industrial sewing machines, start-stop operations are extremely frequent, with the result that the clutch-brake unit is always slipping either on the clutch side or on the brake side, i.e., it becomes very hot in operation. The result is that the brake facings and especially the clutch facings swell up, i.e., undergo a thermally caused expansion. This is true especially of the cork facings and linings used for the sake of their long useful life. In order to have sufficient clutch clearance, and sufficient brake clearance in the case of brakes, after the brake facing and clutch facing have swollen up, the clutch clearance and the brake clearance must be made relatively great while the drive is cold. As a result, however, when braking is abrupt, i.e., when the clutch or brake disk comes out of engagement with the flywheel and into engagement with the opposite brake bearing, impact noises are produced. To suppress this noise in the drive according to DE-OS No. 32 23 379 (corresponding to U.S. Pat. No. 4,556,132) which describes this class of drives, a thermally sensitive adjusting means is provided for the automatic adjustment of the clutch clearance by shifting the flywheel and clutch-brake disk relative to one another. Such an adjustment by a thermally sensitive adjusting means is a good basic solution to the problems described, but since the heat has to be conducted away from the point where it develops, to the thermally sensitive adjusting means, especially between the clutch facing and the clutch surface on the flywheel, errors, and especially a certain lagging of the system, are unavoidable.
The invention is therefore addressed to the problem of configuring the drive such that, by means of especially simple design, the impact noises which occur when a braking action is initiated will be suppressed.